CRAIG, Colo. (AP) - Mitt Romney is poised to clinch the Republican presidential nomination after Tuesday's Texas GOP primary, a largely uncontested election that will formalize the former Massachusetts governor's status as President Barack Obama's general election challenger.
While Romney's nomination has been virtually assured for a month, the day marks the culmination of several years of work, dating back to his unsuccessful 2008 effort, and perhaps far earlier.
"It'll be a big day tomorrow," Romney told reporters aboard his campaign plane Monday evening.
"I'm looking forward to the good news." But Romney's focus Tuesday will be hundreds of miles north of Texas, where he's scheduled to court voters and donors in Colorado and Nevada during a two-state swing punctuated by a Las Vegas fundraiser with conservative businessman Donald Trump.
The evening event, set for the Trump International Hotel, comes amidst fresh criticism from Republicans and Democrats over Trump's continued questioning of Obama's citizenship.
Romney hasn't condemned Trump's false claims, offering a fresh example of the presidential contender's reluctance to confront his party's more extreme elements.
There have been other examples in recent weeks that underscore Romney's delicate push to win over skeptical conservatives while appealing to moderates and independents who generally deliver general election victories.
Asked Monday to weigh in on Trump's support for the so-called birther movement, Romney declined to condemn Trump's latest suggestion that Obama was born in Kenya.
"I don't agree with all the people who support me. And my guess is they don't all agree with everything I believe in," Romney told reporters before flying from California to Colorado Monday evening. "But I need to get 50.1 percent or more. And I'm appreciative to have the help of a lot of good people."
Polling suggests that the election between Romney and Obama will be very close, ultimately decided by several swing states, Colorado and Nevada among them.
Romney will begin campaigning Tuesday in the northern Colorado town of Craig before flying to Las Vegas for an afternoon rally before the Trump fundraiser.
The Texas primary offers 152 delegates; Romney is just 58 delegates shy of the 1,144 needed to become the nominee.
His Republican rivals Rick Santorum and Newt Gingrich already have endorsed Romney, while Texas Rep. Ron Paul has stopped actively campaigning.
Gingrich is expected to attend the Trump fundraiser.
Under similar circumstances last week, Romney swept all the delegates in GOP primaries in Kentucky and Arkansas and picked up more endorsements from party leaders.
But Romney's meeting with Trump may generate as much interest, or more, than his tightened grasp on the Republican nomination.
"I do not understand the cost benefit here," conservative commentator George Will said over the weekend. "The cost of appearing with this bloviating ignoramus is obvious, it seems to me."
"Donald Trump is redundant evidence that if your net worth is high enough, your IQ can be very low and you can still intrude into American politics," Will continued. "Again, I don't understand the benefit. What is Romney seeking?"
Trump revived the false claims about Obama's birthplace late last week, citing a discredited story about a literary agency that mistakenly listed that Obama was born in Kenya.
While Romney briefly addressed the issue Monday, his senior aide Eric Fehrnstrom also declined to condemn Trump's remarks in a recent interview.
"I can't speak for Donald Trump ... but I can tell you that Mitt Romney accepts that President Obama was born in the United States," Fehrnstrom said. "He doesn't view the place of his birth as an issue in this campaign."
Romney has been criticized on several occasions for failing to speak out against extreme rhetoric from his party.
The reluctance stands in contrast to the 2008 GOP presidential nominee and current Romney supporter, Sen. John McCain, R-Ariz., who once corrected a supporter who called Obama a Muslim.
Campaigning in Cleveland earlier in the month, Romney did not initially respond to a supporter who suggested that Obama should be tried for treason.
He said after the rally that he didn't agree. He was also slow to condemn conservative radio host Rush Limbaugh, who said a college student defending Obama's contraception policy was "a slut."
At the time, Romney initially declined to weigh in on the issue before saying "it's not the language" he would have used.
And he was initially silent on violent rhetoric from classic rocker Ted Nugent before a spokeswoman said Romney "believes everyone needs to be civil."