If you are wondering where your tax rebate check is — you know, the big promise from the economic stimulus package being developed in Washington — don't hold your breath.

It's stuck in the Senate as members, Republican and Democrat alike, are arguing over what to add to the version that passed last month in the House. Lawmakers still hope to get a bill to President Bush by Feb. 15, but that date is fast-approaching.

A vote is scheduled Wednesday evening, but if past is prelude, anything can still happen.

Senate Democrats want a much larger package than what the House sent them — some $40 billion more — to extend unemployment insurance benefits, and also give checks to low-income seniors and disabled veterans by counting Social Security as earned income.

The Senate Democrat version would also provides energy tax credits for the biofuels and coal industries, and provide larger tax rebate checks to more Americans.

One problem: That bill only received three Republican votes when it passed last week out of the Senate Finance Committee, 14-7.

Some Republicans in the Senate are caving to mounting pressure from powerful lobbying groups — like AARP — and have budged to support the additions that would benefit seniors and disabled vets. But they haven't agreed to the other, wider Democratic provisions.

To add another wrinkle, Senate Minority Leader Mitch McConnell, R-Ky., told reporters he is crafting his own amendment to the House-passed bill. The bill would include seniors and vets, but he would keep the overall cost of the stimulus package to about $150 billion — roughly the cost of the House version, and about 1 percent of U.S. gross domestic product, a number Bush was aiming for.

McConnell's plan would add the groups without adding to the price by trimming down the size of the rebate checks to $500 for individuals making less than $75,000; $1,000 for married couples making less than $150,000.

But even Democrats don't appear to be standing on firm ground on the package. Senate Majority Leader Harry Reid, D-Nev., also has taken a different tack in recent days.

Just Thursday, Reid told reporters he wanted to see seniors and vets added, at the very least, to the House bill.

Reid's Finance Committee Chairman, Max Baucus, D-Mont., delivered an impassioned speech on the floor that day calling for this addition, if nothing else.

But five days later, on Tuesday, Reid said members only get one bite of the apple: It's the Finance Committee package — with all the bells and whistles — or nothing. He said he would not hold a vote on the pared-down version that would only add seniors and veterans.

Why the about-face? Reid told reporters it resulted from "when we finally saw in black and white that there was a significant increase in unemployment (from last week's new Labor Department statistics) and we saw the tremendous outpouring of support from around the country for the unemployment benefits extension, (and from) the business community, which has wrapped their arms around this package.

"I think the package is pretty good. We should go for the whole package, rather than pick and choose [seniors and vets]."

In light of last week's quick-change on policy, reporters quizzed Reid Tuesday on whether it was a posture that would eventually lead back to the stripped-down, vets-and-seniors-only package. Hedismissed the notion.

"I think that if they think this is a bluff, wait until we have this vote and they'll find out if it's a bluff. I'm not much of a bluffer," Reid said.

For the critical test vote coming up Wednesday evening, Democratic presidential hopefuls Barack Obama and Hillary Clinton are expected to return for the vote to help boost its chances of survival.

Meanwhile, AARP took a poll over the weekend showing 90 percent of Americans surveyed agreed seniors should receive rebate checks. It remains to be seen if the Finance Committee package will pass. It is not expected to, possibly falling as little as two votes short.

Nevertheless, AARP is working hard alongside other business, financial, and mortgage interest groups to garner enough votes for the Democrats' measure.

"We're not taking any vote for granted, but we're optimistic that the Senate will pass the Baucus-Grassley package," AARP spokesman Jim Dau told FOX News.