Harry Reid believes in being blunt.

With an economic stimulus package hanging in the balance, the Senate majority leader warned Republicans they would have just one chance to support rebates for 20 million senior citizens and 250,000 disabled veterans as part of a broader Democratic package.

“Well, 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,” Reid said on Feb. 5. “I’m not much of a bluffer.”

Two days later, after Democrats fell one vote short of the 60 needed to advance the measure, Reid caved. He allowed a vote on a narrow amendment that expanded eligibility to senior citizens and veterans but dropped a number of the provisions that Democrats wanted and Republicans opposed.

Republicans made a note of Reid’s poker-playing skills.

“Phil Gramm … said, ‘Never take a hostage you’re not ready to shoot,’ ” Senate Minority Whip Jon Kyl (R-Ariz.) said, referring to the former Texas GOP senator. “And obviously, Harry took some hostages that at the end of the day he wasn’t willing to shoot.”

Since taking one of the toughest jobs in Washington last year, Reid has balanced tough talk with a demonstrated expertise in Senate procedures. He has used arcane rules to try to fend off controversial amendments, prevent White House recess appointments and advance his party’s agenda in a narrowly divided chamber where each senator has extraordinary power to influence the process.

Yet his blunt manner and empty threats may prove to be an Achilles heel. Republicans say Reid’s reputation for backtracking from firm lines he’s laid down is a weakness that they could exploit in the final year of the 110th Congress.

They offer his actions on some of the biggest issues of the year — Iraq war funding, the economy and immigration legislation — and also his repeated veiled threats for holding weekend votes.

“All of that goes to his credibility,” Kyl said. “And he wants to have the maximum credibility since he’s obviously the majority leader. So he’ll want to think about that in the future.”

A majority hardly ensures leverage in a Senate where Democrats hold 51 seats yet 60 votes are needed to move legislation and 67 votes are needed to override a presidential veto. Democrats say Republican roadblocks leave Reid with no choice but to use threats as a last resort to try to chip away at GOP opposition.

“I think he knew exactly what he was doing, which was to do everything he could to get the 60th vote,” Sen. Charles Schumer (N.Y.), vice chairman of the Democratic Conference, said of Reid’s threat over the economic stimulus package.

That threat put heavy pressure on Sen. George Voinovich (R-Ohio) to back the Democrats’ plan, but he ultimately decided instead to support the more targeted amendment. He said that Reid’s tactics were not enough to sway him.

“I think it’d be very much better off if they get in the room [and negotiate] instead of . . . playing Russian roulette,” said Voinovich, who also complimented Reid for compromising.

In a brief interview, Reid rejected the notion that he was losing credibility by walking away from ultimatums, saying Republicans would pay the price for their votes.

“They can go home and explain to all their constituents how they voted against senior citizens [and] how they voted against people who need unemployment benefits, the homebuilding industry, and … everything else,” Reid said. “They have to go home and explain that. I don’t. I voted for it all.”

His spokesman, Rodell Mollineau, said that Reid makes “no apologies” for his threats, saying that on the economic measure, he forced Republicans against their will to accept rebate checks for senior citizens and disabled veterans.

Reid may see the value in making threats both on political and policy levels. The threats sometimes force Republicans to capitulate, or at least move toward his positions.

When Reid said that former Bush attorney Ted Olsen would not be confirmed if he were nominated for attorney general, the White House declined to propose him.

The prospects of having a Democrat in the White House next year could be the reason that Reid often takes a position that generates solid GOP opposition and shows a clear distinction between the two parties.

Late last year, when the White House was clamoring for more Iraq money, Reid repeatedly warned that President Bush would not get war funding if he and the GOP did not accept a timetable for bringing troops home.

Most Republicans, including ones in tight reelection races, voted to keep troops in Iraq despite the unpopularity of the war. Democrats backed away from Reid’s threat and gave the White House $70 billion more with no strings attached.

And during a volatile immigration debate that occupied several weeks last spring, Reid was able to show a greater split between Republicans than in his own party before the bipartisan legislation ultimately fizzled.

“Harry does his best under extraordinarily tough circumstances. When you faced a record-breaking number of filibusters, you have to try some way to make the Senate move forward,” said Reid’s deputy, Senate Majority Whip Dick Durbin (D-Ill.).

Sen. John Cornyn of Texas, the Republican Conference vice chairman, said making threats isn’t enough to win GOP support.

“He really doesn’t have that much leverage,” Cornyn said.

J. Taylor Rushing contributed to this article.