Tourists flock to memorials in Washington on Saturday, October 19, the first weekend after the end of the partial government shutdown. The Washington Monument and other landmarks across the country have reopened to the public after the 16-day shutdown. The government impasse ended when President Barack Obama signed a spending and debt ceiling agreement that Congress passed, averting a possible default. 
The giant panda Tian Tian keeps schoolchildren entertained at the National Zoo in Washington on Friday, October 18. 
A visitor checks out art in the Hirshhorn Museum and Sculpture Garden in Washington on Thursday, October 17. 
The Smithsonian Institution's National Museum of American History on the National Mall is back in business October 17. 
A U.S. park ranger helps a tourist at the Martin Luther King Jr. Memorial in Washington on October 17. 
Park rangers are on duty at the Lincoln Memorial on October 17. 
People line up for tickets to visit Alcatraz Island in San Francisco Bay on October 17. 
Museum specialist Richard Doerner winds the historic timepiece known as the Ohio Clock outside the Senate chamber on October 17. The clock stopped during the 16-day shutdown when federal workers were furloughed. 
Visitors to the U.S.S. Constitution walk up the gangplank for a tour in Boston on October 17. 
Tourists gather at the Martin Luther King Jr. Memorial in Washington on October 17. 
Visitors enter the Smithsonian Institution's Air and Space Museum in Washington on October 17. 
A worker blows leaves away from the Russell Senate Office Building in Washington on October 17. 
A tour guide leads tourists through the U.S. Capitol Rotunda on October 17. 
A worker cleans the fountain at the National World War II Memorial in Washington on October 17. The Lincoln Memorial is in the background. 
Barricades used to close the Martin Luther King Jr. Memorial during the shutdown lie dismantled October 17 in Washington. 
Vice President Joe Biden greets Environmental Protection Agency workers with muffins at the Clinton Federal Building in Washington as they return to work October 17. 
U.S. park ranger Richard Trott picks up closed signs at the Lincoln Memorial after it reopens October 17. 
Washingtonians head to work near Pennsylvania Avenue on October 17 as federal workers return in force to their jobs after the shutdown. 
U.S. Park Service workers remove a barricade from the Martin Luther King Jr. Memorial in Washington on October 17. 
A National Park Service ranger takes down a notice about the government shutdown at the Liberty Bell Pavilion in Philadelphia on October 17. 
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- David Frum: Twice Washington has come to the edge of default
- Extreme politicians in either party could trigger another potential default, he says
- Reforms could eliminate that possibility, by removing debt ceiling, Frum says
- Frum: Give party leaders more power to keep their members in line
Editor's note: David Frum, a CNN contributor, is a contributing editor at The Daily Beast. He is the author of eight books, including a novel, "Patriots," and a post-election e-book, "Why Romney Lost." Frum was a special assistant to President George W. Bush from 2001 to 2002.
(CNN) -- Twice in two years, the United States has teetered on the verge of a catastrophic default: once in summer 2011, again in fall 2013.
In 2011, default was averted when President Obama yielded significant concessions to Republicans in Congress. In 2013, it was the Republicans who yielded. If these confrontations continue, however, someday somebody will miscalculate, and over the edge the whole world will go.
I won't take time here to parse precisely how bad such a catastrophe would be: worse than 1931? or merely another 2008? All agree it would be very, very bad. And it should be a rule of politics that very, very bad ought to be avoided -- all the more so when it can be avoided very, very easily.
In 2011 and 2013, the people forcing the catastrophe happened to be Republicans confronting a Democratic president. Next time, however, they might well be Democrats seeking leverage against a Republican president.
Over the past dozen years, both parties have become more militant in the way they play politics. If the Republicans look more extreme today, it's also true that they are the party out of power. Wait until it's the Democrats turn to go out, and see how they act.
Yet there are Americans worried by the radicalization of the country's politics. They belong to both parties and to neither. They recognize that something is going seriously wrong -- and that this trend could have serious consequences. Here are some ideas that such Americans might want to consider. I'll start with the easiest first, then work up to the more ambitious:
1) Abolish the debt ceiling.
McCain: Shutdown tactics 'fool's errand' 
GOP strategist: This has hurt the brand 
Sen. Cruz: GOP failed, 'didn't unite' The debt ceiling is an artifact of the First World War. In the 19th century, Congress authorized each and every bond issue by the United States. The costs of global war rendered that practice untenable, so instead Congress granted the executive branch a generalized authority to borrow up to a set amount.
It seemed a good idea at the time. In the modern context, however, the debt ceiling creates very negative incentives for Congress. Congress can first vote to create a deficit, then vote to refuse to cover that deficit. Remember, it's Congress that sets the level of tax. It's Congress that sets the level of spending. If Congress is unhappy about the difference between those two levels, Congress has the power to close it. There's no need to threaten to blow up the financial world.
Four things we learned from government shutdown
2) Reform campaign finance to strengthen party leaders.
The Republicans who pushed this latest crisis were challenging their own party leaders fully as much as they were challenging President Obama. Speaker John Boehner has repeatedly made clear his dislike for debt-ceiling extortion. Yet he has lacked the power to stop it.
TV commentators snark at Boehner's weak hold on his caucus. Who else would do better? Boehner lacks sticks and lacks carrots. He doesn't choose committee chairs. He does not dispense pork barrel favors. He can't strip a recalcitrant member of his or her Republican nomination at the next primary. Most crippling of all, and quite unlike the powerful speakers of former times, he does not control access to party funds.
In most democracies, most political money is raised and spent by party leaders. The United States, by contrast, has built a uniquely candidate-centered fundraising system. This system has gradually accreted over the past 70 years, the byproduct of restrictions by reformers and innovation by nonparty groups.
The party-dominated politics of 1830-1970 had a lot of problems, no doubt. But the post-party politics since 1970 has delivered even worse results. One reform would make a big and immediate difference: Lift the cap on the maximum amount parties can give to their candidates: today only $5,000 per House candidate -- unchanged since 1940 -- plus an additional $42,000 of party-coordinated funds.
Right now, a sufficiently obtrusive House member doesn't have much to fear from defying Boehner. (In the last midterm election cycle, Boehner and his leadership PAC together raised less money than GOP outlier Michele Bachmann.) If, however, the speaker could open or close a million-dollar contribution spigot, that member would listen as attentively as the members used to listen to House Speaker Sam Rayburn -- and might turn a deafer ear to Heritage Action when it proposes to blow up the world to score a point.
GOP, Boehner take shutdown hit in new CNN poll
3) Make continuing resolutions automatic.
The United States is not the only country to have budget disputes. Other democracies cope with these inevitable disagreements by the simple rule: If no budget can be agreed, simply carry over the previous year's budget month by month until agreement is ultimately reached. While politicians negotiate, travelers can still renew their passports. Obvious, no? Why not here?
The fact is, most of the time, Americans already do this. Formal budgeting tends to sputter to a halt in periods of divided government. The continuing resolutions that fund the federal government were invented as exactly the kind of work-around that other democracies use. So let's ensure that the continuing resolutions continue when they are needed most, when the differences seem most acute. The whole point of democracy is that there are no disagreements so acute that they are worth overthrowing the government and the state.
And indeed, when disagreements do reach the ultimately dangerous point, somebody will blink (usually the somebody doing worse in the opinion polls). Why let things reach that point in the first place?
The short answer is that there are political factions that value conflict almost as an end in itself. But most people don't -- and the more explicitly the questions are raised, "Should the government function?" and "Should government pay its bills in full and on time?" -- the larger the constituency we can amass for simple reforms to make government work for all who pay for it.
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The opinions expressed in this commentary are solely those of David Frum.
