Senate Majority Leader Harry Reid may yet rue the day he helped popularize the phrase “The Party of No.” It never did stick to Republicans. But it may be about to become a very catchy description for the Democratic Party.

This week’s news is the incoming House GOP majority and its sweeping reform plans. Next week’s news (and the news for most weeks thereafter) will likely be the many ways Mr. Reid goes about killing those reforms. Day after day, week after week, the House will be sending to the Senate bipartisan bills to cut spending, to make smart fixes to ObamaCare, and to rein in the federal government. And day after day, week after week, Mr. Reid will likely be cementing his party’s reputation for blocking, obstructing and deterring nearly every one of them.

If that’s the road he travels, the label will stick this time. Democrats were unable to tar Republicans as the “Party of No” for a simple reason: The American public wanted the GOP to halt the Obama agenda. As Senate Minority Leader Mitch McConnell famously noted, “It depends on what you are saying ‘no’ to.”

In this case, Mr. Reid—the public face of his party—will be saying no to exactly the reforms Americans voted for in the midterms. If Mr. Reid is wondering what happens to Senate Democrats who condemn popular reforms to the legislative graveyard, he could call Tom Daschle. The one-time majority leader lost his own seat in 2004 after his constituents tired of his obstructionism.

Mr. Reid isn’t up for re-election in 2012, but 23 members of his caucus are. A chunk hail from red states; a bigger chunk won their states only narrowly in 2006. Most had the Cheez Whiz scared out of them by the recent midterms, and their priority is retaining their jobs. As Missouri’s Claire McCaskill noted recently, any Senate Democrat who claims not to be worried about 2012 ought to be hooked to “a lie-detector machine.”

They know what’s coming. The focus right now is on the comprehensive repeal of ObamaCare that House Republicans will pass next week. Mr. Reid will kill the repeal, and most Senate Democrats will support him. What gives the vulnerable Senate 23 the willies is what follows.

Once full repeal goes nowhere, House Republicans (joined by some Democrats) will begin sending the Senate smaller repeal bills. The House will pass legislation getting rid of the highly unpopular individual mandate. It will axe unpopular, punitive health-care regulations on business. It will roll back unpopular ObamaCare taxes. Nervous Senate Democrats are already running for cover. Ms. McCaskill this week said she’d consider joining Republicans to scrap the individual mandate if it could be replaced with a “viable” alternative.

And so it will go. House Republicans will send the Senate a weekly spending cut measure. They will send micro-targeted bills to stop job-killing EPA rules, to provide tax relief, to cut back regulations, to reform the worst parts of the Dodd-Frank Wall Street law. The bills will directly relate to jobs in the home states of many vulnerable Democrats, who will be under enormous pressure to get on board.

Their support may, paradoxically, make it less likely Mr. Reid brings any of the bills up for a vote. For every vulnerable 2012 member, Mr. Reid has a safe liberal member demanding he not bend. More notably, he’s got a president to keep in the White House. And Mr. Obama remains vehemently opposed to most GOP reforms.

If Mr. Reid does let GOP reforms proceed, some Democrats will join Republicans in voting for them. That puts President Obama in the embarrassing position of having to veto “bipartisan” legislation. The president is counting on Mr. Reid not to let this happen, to be his veto pen, and Mr. Reid’s own philosophical inclinations qualify him for that role. And so even as the House GOP basks in the glow of its new, more transparent rules, Mr. Reid will be resorting to all manner of filibusters and procedural tricks to prevent Senate Republicans from forwarding any measure or amendment that could attract Democratic support.

That isn’t to say there won’t be compromises. Mr. Obama knows it is in his interest to choose areas of cooperation. The White House has already agreed changes are necessary for ObamaCare’s 1099 tax reporting requirements. It will probably pick some individual spending cuts to support. This week it floated the idea of a corporate tax reduction compromise. All of these will be a green light for Mr. Reid to hold votes.

But these areas of cooperation will be swamped by the flood of House measures Mr. Reid will likely bury. He will try to blunt the headlines by driving the administration’s own agenda out of the Senate. Then again, it isn’t clear Mr. Reid knows what that agenda is. Come Monday, the Senate is already going on a two-week recess.

Barring a more dramatic White House shift to the middle, the ground is being laid for the president and the majority leader to hold hostage all manner of legislation that will have the support of the public and bipartisan majorities. It won’t be all Democrats who are responsible, but it will be all Democrats tagged as the new “Party of No.”

Write to kim@wsj.com