His poll numbers may be sinking, but six months into his presidency, Barack Obama retains the admiration and the trust of voters. To be sure, they're not as admiring of his policies. The attacks from critics about unsustainable debt and big government have taken their toll. Voters question whether his policies will work, and the legions of progressives who backed him wonder whether he has what it takes to work his will on Capitol Hill.

White House officials say with some pride that Obama doesn't draw lines in the sand. Maybe he should. If political capital is measured by popularity, Obama still has plenty. What he doesn't seem to have is a willingness to spend it. With health-care reform working its way through Congress and climate-change legislation within reach for the first time ever, it's time for Obama to get in touch with his inner LBJ, but so far the signs don't look good.

Obama's Zen-like avoidance of confrontation gives way too much leeway to Democrats. A case in point is New Jersey Sen. Robert Menendez's moves to block the nomination of Carlos Pascual to be ambassador to Mexico, first reported in the Mexican press. Using his senatorial prerogative, Menendez can put what's called a "hold" on the nomination. The Cuban-born Pascual helped write a report while at the Brookings Institution, a liberal think tank, urging normalization of relations with Cuba at the conclusion of a three-stage process. Menendez, the son of Cuban immigrants, is virulently antinormalization and takes it out on Obama initiatives that touch on Cuba, however tangentially.

Meanwhile, Mexico is on the verge of becoming a failed state with its weakening economy, a violent drug war, and the looming threat of another deadly outbreak of the H1N1 flu in the coming months. It's an important country with implications for U.S. national security, and the administration needs a capable ambassador there. Why should the U.S.-Mexico relationship bear the burden of one senator's antiquated position on Cuba? Can't Obama bring the hammer down on recalcitrant Democrats like President Johnson would have done?

This kind of tit for tat goes on all the time in Congress, and the way a Hill veteran explained it to me, Obama's reluctance to take on Menendez stems in part from wondering what demands the senator might make in return, and is it worth giving him a political IOU to cash in for who knows what? When I point out the Founding Fathers designed our system so that a single senator could have this power, he quipped that "Florida should have two senators, not three." A spokesman for Menendez says a hold cannot be placed on the nomination until it is voted out of committee, and it's the senator's policy to not comment on holds, his or anybody else's.

It's not Obama's temperament to lean hard on people, and he doesn't know his prey the way President Johnson did as a former Senate majority leader. LBJ had compromised and bullied and legislated for years, and he knew everybody's sweet spot, when to cajole, when to threaten. Obama's got Rahm Emanuel, a cleaned-up, not-quite-so-vulgar version of Johnson. It's not the same, but will have to do. With unemployment climbing and 12,000 people a day losing health insurance, Obama cannot allow universal health care to slip away yet again. If a Democratic president with commanding majorities in both the Senate and House can't make it happen this Congress, the Democrats will take a hit in the 2010 congressional election, and the losses will be deserved.