Washington ? Partisanship is reaching new heights in Washington, even as President Barack Obama makes almost daily pleas to get along.

He’s scheduled a bipartisan health care summit, and just Tuesday he hosted GOP leaders at the White House for the first time in two months.

But he often undercuts his overtures with his own jabs at Republicans. And there’s little indication the GOP is taking his comments as anything but political.

Both sides’ stances might be summed up this way: We’re ready to cooperate right now. All you need to do is go along with what we want.

On Capitol Hill, the minority Republicans routinely require a super-majority (60 votes out of 100) to move Senate bills. And only one GOP lawmaker, a House member, voted for the landmark health care bills approved separately by the House and Senate in December.

The Democrats, meanwhile, wrote the House and Senate health care bills with virtually no input from Republicans.

How has this come about? The contributing factors have been accelerating and converging for years: Gerrymandered House districts. Political realignments that drive Democrats from the South and Republicans from the Northeast.

And perhaps most of all: greater mobilization by both parties’ ideological wings, who punish those who dare cooperate with the other side.

House and Senate members once saw the opposition party as the adversary, but now they consider it the outright enemy, said Norman J. Ornstein, a congressional scholar at the American Enterprise Institute.

Americans “are dividing into tribes more than we did before,” he said. Voters have driven virtually all liberals out of the Republican Party and all conservatives from the Democratic Party, eliminating a political dynamic that helped enact major legislation such as civil rights and Medicare in earlier decades.

Obama made a multi-pronged appeal for bipartisanship Tuesday. He hosted Republican congressional leaders at a meeting on jobs, then held an unannounced news conference to ask for greater Democratic-GOP accord on at least a half dozen issues.

But any doubts that bare-knuckled partisanship still grips Washington were diminished when Republican leaders stepped outside the White House and denounced Obama’s health care plan, even suggesting they might not attend his Feb. 25 summit.

Tuesday was a perfect example of high-minded appeals for cross-party cooperation being quickly undermined by barbs. Obama and Republican leaders couldn’t even agree on a definition of bipartisanship.

“Bipartisan cannot mean simply that Democrats give up everything that they believe in, find the handful of things that Republicans have been advocating for, and we do those things, and then we have bipartisanship,” Obama told reporters. “There’s got to be some give and take.”