(Adds details, comments from Obama's Idaho visit)
By Jeff Mason
BOISE, Idaho, Jan 21 (Reuters) - A day after delivering a defiant State of the Union speech to the Republican-led U.S. Congress, President Barack Obama headed to the conservative heartland on Wednesday to promote his plans for bolstering the middle class.
Obama left Washington for a two-day trip to Idaho and Kansas to push his message that everyone should stand to gain from an economy that has all but recovered from years in the doldrums.
No longer restrained by having to face an election again, Obama struck a confident tone in his State of the Union address on Tuesday night, saying, "the shadow of crisis has passed."
Despite losing control of the Senate to Republicans in November's midterm elections, Obama has taken an active role setting the agenda on policy from immigration reform to improving relations with Cuba, as he seeks to shape his legacy.
Polls show Obama has reason to be upbeat. Reuters/Ipsos polling data on Wednesday put his approval at 41 percent this week, up four points from a month ago. But 52 percent of Americans still disapprove of his performance.
To a crowd of more than 6,000 in a stadium at Boise State University, Obama continued to chide Republicans and noted that their limited applause during his speech on Tuesday made clear that they did not back his ideas.
"I know there are Republicans who disagree with my approach. I could see that from their body language yesterday," he said to laughter from the crowd.
"My job is to put forward what I think is best for America. The job of Congress, then, is to put forward alternative ideas, but they've got to be specific. They can't just be, 'no.' ... Tell me how we're going to do the things that need to be done. Tell me how we get to 'yes.'"
Republicans have not warmed to Obama's proposals to finance free community college or raise taxes on wealthy individuals, and they are not pleased by his veto threats.
Obama pledged to veto Republican efforts to overturn his signature healthcare law, executive action loosening rules for undocumented immigrants, and efforts to force the White House to approve the controversial Keystone XL oil pipeline.
Republicans called for Obama to be more humble, given that they took control of both chambers of Congress this month after winning the midterms handsomely.
"We've only been here 2-1/2 weeks, and he's put seven veto threats. I think that's probably not the best start. Let us work the legislation before you decide something's going to be vetoed," House of Representatives Majority Leader Kevin McCarthy said on the CBS "This Morning" program.
One area where Obama might win support from Republicans is on trade. He called in his speech for Congress to give him so-called fast-track authority to help complete major trade pacts such as the Trans-Pacific Partnership deal being negotiated with Asia.
He warned that China would be the winner if that deal falters.
"The president made very clear last night that TPA (Trade Promotion Authority) and TPP is now a top presidential priority and now is the time to get it done," said Evan Medeiros, the top White House aide on Asia.
While some conservative Republicans oppose giving Obama fast-track authority, the heaviest resistance might be from fellow Democrats who worry that trade deals could hurt American workers.
McCarthy said Republicans are also willing to work with Obama on tax reform.
Treasury Secretary Jack Lew said on Wednesday that after recent talks with Republicans he was confident a business tax reform plan can make it through Congress. Lew put the chances of passage at "better than 50-50."
The tax plan includes a lower top corporate rate, ensuring more taxes are paid on foreign earnings, and closing a host of loopholes.
In Idaho, Obama visited a lab at the university's Micron Engineering Center, telling students and staff that he was good at engineering despite not having studied it. The White House chose Boise because of its tech sector and record in training for tech jobs.
Both Idaho and Kansas, where Obama traveled to for the night, are "red" or Republican-leaning states. The White House chose states deliberately to show that Obama's policies have bipartisan appeal.
Obama's vision of a stronger and more expensive safety net stands little chance of becoming law this year, but it could shape the debate for the 2016 presidential election.
Hillary Clinton, the likely frontrunner for the Democratic nomination, is already facing heat from Massachusetts Senator Elizabeth Warren and others on the left, who worry Clinton may bow to pressure from Wall Street and not push enough of a populist agenda on the economy.
In a post on Twitter after the Tuesday speech, Clinton wrote: "@BarackObama #SOTU pointed way to an economy that works for all. Now we need to step up & deliver for the middle class. #FairShot #FairShare". (Additional reporting by Julia Edwards, Doina Chiacu, Jason Lange, Howard Schneider, Susan Heavey, Krista Hughes and Richard Cowan; Writing by Alistair Bell and Jeff Mason; Editing by Ken Wills)