Donald Trump looms behind speecehes from both Obama and Nikki Haley

Donald Trump was not in the room during President Barack Obama's final State of the Union speech, but the Republican presidential front-runner held the center of attention nonetheless.

Both Obama's speech on Tuesday, and for that matter, the Republican response by South Carolina Governor Nikki Haley, took pains to rebuke Trump, the real-estate mogul whose red-hot rhetoric has endeared him to some and dismayed others in the campaign for the Nov. 8 presidential election.

Obama and Haley, although from different parties, offered a defence on Tuesday of establishment politics, a plea for optimism and a quest for common ground. Obama seemed to refer specifically to Trump's call for a temporary ban on Muslim immigration following a deadly shooting attack last month in San Bernardino, California, by a couple authorities said had been radicalised.

The president said: "We need to reject any politics that targets people because of race or religion. This isn't a matter of political correctness." Trump has mounted much of his insurgent candidacy on the notion of America losing ground, both economically and in terms of global influence. Obama rejected that idea outright.

"It's easier to be cynical," Obama said, "to accept that change isn't possible, and politics is hopeless, and to believe that our voices and actions don't matter." Soon after Obama concluded his remarks in the chamber of the US House of Representatives, Trump tweeted: "The State of the Union speech was one of the most boring, rambling and non-substantive I have heard in a long time."

While consistently criticising Obama's record, Haley, seen as a potential Republican vice presidential choice for the November election to replace Obama, also seemed to indict Trump's message without naming him.

"Some people think that you have to be the loudest voice in the room to make a difference," Haley said. "That is just not true. Often, the best thing we can do is turn down the volume. When the sound is quieter, you can actually hear what someone else is saying. And that can make a world of difference."

Paul Sracic, chairman of the politics department at Youngstown State University in Ohio, said: "Donald Trump must be smiling tonight. He managed to make himself the target of not just the president's State of the Union address, but also the Republican response. "Trump, and in particular his views on immigration, are now dominating our political discourse in a way that no one would have predicted even a year ago."

CRUZ WEIGHS IN

Obama also appeared to single out conservative Texas Senator Ted Cruz, the top challenger to Trump in the Republican race. Cruz has called for a massive bombing campaign in Iraq and Syria to wipe out Islamic State forces.

Meeting the threat of Islamic State, Obama said, "needs to be more than tough talk or calls to carpet-bomb civilians." Democratic strategist Brad Bannon said Obama "made the argument very well that leadership is not bombing the crap out of someone."

Cruz quickly countered in a statement. Obama, he said, "lectures us on civility yet he has been one of the most divisive presidents in American history." Both Trump and Cruz, who are topping opinion polls weeks before the early nomination contests in Iowa and New Hampshire, have pledged to push the Republican Party in a more confrontational direction, and seek to undo much of what Obama has accomplished as president.

Both candidates are likely in coming days to hammer the Obama administration on its approach to Islamic State. Republican strategists keyed on Obama's statement that the militant group was not a threat to "our national existence" and cited the detention by Iran of 10 US Navy sailors after two ships were reported to have crossed into its territorial waters.

"Republicans will disagree with the president that our enemies are not getting stronger and will likely quickly cite Iran has 10 American sailors in its possession at this very moment," said Republican consultant Ron Bonjean.

Obama did not address the sailors' detention in his speech. The White House expects the situation to be resolved quickly. Obama's defence of pragmatic politics may also help his former secretary of state, Hillary Clinton, who is trying to stave off a challenge from self-described democratic socialist Bernie Sanders in the Democratic presidential contest, said Bannon.

"He's talking about holding up the establishment," he said. "When the president makes a good case, it helps Hillary more than Bernie." But John Geer, an expert on voter opinion at Vanderbilt University, thought Obama, in his bid for unity, damaged Clinton's prospects by not making a stronger case for continuing the Democratic agenda. "He didn't put forward an argument why there should be another Democrat for four years," Geer said. "I think she would have liked to see that."