Although the polls are still in flux, it looks increasingly likely that Republicans will win a big victory next Tuesday. But that doesn’t mean that Americans have fallen in love with them.

In fact, even as voters prepare to put Republicans in charge of the House and possibly even the Senate, polls show the Republican party to be only slightly more popular than used-car salesmen. A recent Pew poll showed that only 24 percent of voters approve of Republicans in Congress.

Therefore, if this election is going to be the start of a long-term trend and not a one-time blip, the new Republican-dominated Congress is going to have to deliver. In particular, Republicans are going to have to follow through on their promises to reduce government spending and the deficit. Nothing was more central to Republican campaigns this year, and it was a critical issue to the economically conservative, socially moderate suburban voters who backed Democrats in 2006 and 2008 but switched to Republicans this year. But promises of balanced budgets may prove much easier than actual budget cutting.

Of course, the Pledge to America calls for returning some discretionary spending to 2008 levels. But by 2008, spending was already out of control. Moreover, the pledge does not specify exactly which programs Republicans plan to cut. Unfortunately, budgets have to be balanced on specifics, not generalities.

To show just how tough balancing the budget will be, consider an analysis by the National Taxpayers Union Foundation of the budgetary proposals of four Republican candidates: Pat Toomey in Pennsylvania, Carly Fiorina in California, Marco Rubio in Florida, and Mark Kirk in Illinois. Most of their calls for spending cuts (or increases) were too vague to be fully costed out. But once the budget proposals that could be assigned a price tag were added up, Fiorina was the champion cost cutter, calling for a net reduction in government spending of $155 billion. Rubio was close behind with $153 billion. Most of Pat Toomey’s proposals could not be scored, but the cuts that could netted just $2.5 billion in savings. And Mark Kirk would actually increase spending by $734 million.

To be sure, this is a lot better than their opponents. Toomey’s opponent, Joe Sestak, for example, has proposed spending increases of more than $100 billion. But in the face of a $3.55 trillion federal budget and a $1.3 trillion deficit, it’s going to take much bigger cuts than have so far been proposed.

During an election campaign, it is perhaps understandable if candidates avoid specifics when talking budget cuts. After all, every program has a constituency that would be alienated by proposals to cut it. But when Republicans turn from campaigning to governing, they are going to have to make cuts that will offend powerful voter groups. Cuts of the size necessary to balance the budget are going to hurt — simply cutting the usual “waste, fraud, and abuse” isn’t going to get there.

For example, no serious budget cutting can take place without addressing entitlements. Some Republican candidates, including Toomey, Rubio, Ron Johnson in Wisconsin, Joe Miller in Alaska, Rand Paul in Kentucky, and Sharron Angle in Nevada, have shown a willingness to consider some creative ideas for entitlement reform. But the Republican leadership in Washington has not been as brave. The Pledge to America exempts programs for the elderly from the proposed cuts, and congressional Republicans spent much of the debate over health-care reform posing as defenders of the elderly from Medicare cuts. They are going to have to do a lot better than that.

The Pledge also keeps defense spending away from the budget knife. But if Republicans are really serious about balancing the budget, the defense budget is going to have to be on the table. Defense now accounts for nearly 23 percent of all federal spending and more than half of all discretionary spending. The Pentagon should be subject to the same scrutiny as any other government agency. This will require a thorough review of America’s commitments around the world. Slashing spending while continuing our current policies risks leaving our troops stretched far too thin or without the equipment they need. But at a time of massive debt, should we not be asking whether the U.S. really needs to keep troops deployed in 135 countries? Can we afford to fight two wars indefinitely? Shouldn’t countries such as Japan, Germany, and South Korea be asked to pick up more of the cost of their own defense?

If Republicans win this election, it will be because voters recoiled from the big-government, big-spending, big-deficit policies of the Obama administration and congressional Democrats. That was enough for Republicans to gain power this year. If they want to keep it, they are going to have to show the courage to make some very, very tough decisions.