WASHINGTON (AP) — Reps. Barbara Lee and John Fleming are highly dubious at best about President Barack Obama's requests for enhanced powers to make trade deals and to deploy the U.S. military. And that's like oil and water mixing easily.

Ideological chasms usually separate Democrat Lee of California — one of Congress' proudest liberals — and Republican Fleming of Louisiana, among its staunchest conservatives. But they personify Congress' odd left-right coalition that's complicating Obama's bid for two of his priorities.

Like many House Democrats and Republicans, they reached their positions by different paths. Lee says trade deals hurt American workers. And she shares many liberals' aversion to new wars that seem open-ended.

Fleming, meanwhile, doesn't want to cede more power to Obama on any front, because he's still fuming over the president's executive actions on health and deportation policies.

"I'm less willing to give him flexibility in authority than I would most presidents, Democrat or Republican, because of his abuse of authority," Fleming said.

This left-right union requires Obama to seek a large centrist coalition in a Congress whose political "middle" hardly exists anymore.

Many issues, including taxes, spending and immigration, typically split along partisan lines. Trade and warfare do not.

Liberals back Obama on most issues, but scores of them feel snake-bitten by two events of the past 21 years. They contend the 1994 landmark North America Free Trade Act (or NAFTA) led to millions of U.S. jobs going overseas. And they say Republican President George W. Bush misled the nation and Congress when he won approval to invade Iraq in 2003.

Congress voted twice to endorse Bush's military goals after the terrorist attacks of Sept. 11, 2001. Within days of the deadly attacks, lawmakers gave Bush wide leeway to pursue al-Qaida. And in 2002, Congress approved Bush's plan to invade Iraq. That country's much-discussed "weapons of mass destruction" proved not to exist.

Memories of those votes now hamper Obama's request for "authorized use of military force" against terrorists from the so-called Islamic State. His request would leave in place the 2001 war-making authority, which many liberals insist on ending.

Lee calls it "an overly broad blank check" that's used "to keep us in a state of perpetual war."

Trade is another issue that cleaves many liberals from Obama. Like Bill Clinton, he's a Democratic president who supports free trade despite weak support from Democratic lawmakers.

Republicans, meanwhile, call themselves a pro-trade party. But dozens of GOP House members threaten to oppose the White House's trade push because of their animosity toward Obama, not to trade itself.

Obama wants renewal of "fast track" authority, which has let past presidents negotiate trade deals that Congress can ratify or reject, but not amend. A strange-bedfellows force opposes him.

The Communications Workers of America union, which strongly supports Obama on most issues, is working with conservative Republicans to thwart him on trade.

Obama "has consistently broken his trust with the American people on immigration, health care and foreign policy, yet he is now asking for expanded power to negotiate trade deals," says a letter distributed by the union and written by Republican Rep. David McKinley of West Virginia.

A similar letter signed by the Tea Party Patriots and other groups says Obama "has seized power time and again." Denying him fast track authority on trade deals, it says, "sends a clear message that enough is enough."

With many House Democrats abandoning Obama on trade, Republicans must do the heavy lifting to pass fast track and the individual trade deals that presumably would follow. Leading the effort is Ways and Means Committee Chairman Paul Ryan of Wisconsin, the GOP's 2012 vice presidential nominee.

"We see a good team building on this issue," Ryan told Japanese officials during a recent trip to Tokyo. "We're working with Democrats right now" to draft fast-track legislation, he said.

House Democratic leader Nancy Pelosi's liberal leanings align with many colleagues who oppose Obama on trade, but she remains publicly open. "We can find a path to yes," she often says, if certain concerns are addressed.

But assembling centrist House majorities is increasingly difficult.

National Journal's long-running analyses of House votes found a large ideological middle in 1982. Then, 344 House members' voting records placed them somewhere between the most liberal Republican and the most conservative Democrat.

That partisan ideological overlap has shrunk dramatically since then, as the GOP has grown more consistently conservative, and the Democratic Party more consistently liberal. In 2002, the analysis found only 137 House members ranked between the most liberal Republican and the most conservative Democrat.

In 2013, the number was four.

Factors driving centrists from the House include gerrymandered districts; liberals' concentration in cities and the two coasts; and conservative and liberal purists who dominate GOP and Democratic primaries, respectively.