* Former presidents also due to attend dedication
* Memorial service for Texas explosion victims on the agenda
* Fundraiser will aim to help Democrats in midterm elections (Updates with Obama, Bush comments, previous dateline WASHINGTON)
By Steve Holland
DALLAS, April 24 (Reuters) - U.S. President Barack Obama is in Texas to stand shoulder-to-shoulder with former President George W. Bush in what could serve as a powerful reminder of the ongoing struggle against terrorism, from the Sept. 11 attacks to the Boston Marathon bombings.
Obama is due to attend the dedication on Thursday of Bush's presidential library at Southern Methodist University, along with former presidents Bill Clinton, George H.W. Bush and Jimmy Carter and hundreds of Bush administration alumni.
While Democrat Obama and Republican Bush have deep political differences, they share a common belief that the United States must defend itself against violent extremism.
The Sept. 11, 2001, attacks defined Bush's eight years in the White House and last week's Boston Marathon bombing handed Obama another challenge to homeland security.
Obama, at a Democratic fundraiser soon after he arrived in Dallas on Wednesday night, said he was looking forward to attending the Bush library dedication and that he would project a bipartisan spirit.
"One thing I will insist upon is whatever our political differences, President Bush loves his country and loves its people and...was concerned about all people in America, not just those who voted Republican. I think that's true about him and I think that's true about most of us," Obama said.
Bush told ABC News that the Boston attacks reminded him of his time in the presidency.
"I was deeply concerned that there might've been an organized plot," Bush told ABC News. "I don't know all the facts... But I was deeply concerned that this could've been, you know, another highly organized attack on the country. And it still may be. Again, I don't know all the facts."
Certain issues require a common response regardless of political party, said David Yepsen, director of the Paul Simon Public Policy Center at the University of Southern Illinois.
"They may get to the office as a conservative or a liberal but there are real forces that move them to the pragmatic center on a variety of issues and national security is one of them," Simon said.
But Obama was also looking to a time when more Democrats could be elected to Congress. His first stop in Dallas was at a fundraiser that brought in $600,000 for the Democratic National Committee at the home of major Democratic donor Naomi Aberly.
It is his third fundraiser this year for his party in the hope that Democrats can wrestle control of the House of Representatives from Republicans and add to the Democrats' Senate majority in 2014 midterm elections.
Without adding Democratic seats, Obama may find it difficult to overcome Republican opposition to many of the priorities of his second term, such as closing tax loopholes enjoyed mostly by the wealthy and stricter gun control.
"Washington is not, how should I put this charitably, it's not as functional as it could be," Obama said.
Still, he told the Democratic donors, he plans to keep talking to Republicans as he has in recent weeks to try to find common ground, even though "some of you may think I'm a sap" for doing so.
Thursday's dedication of Bush's library and museum has put Bush, the 43rd U.S. president, back in the limelight he has largely avoided since leaving office in January 2009.
At the time, the United States was laboring under the burden of two wars and a collapsed economy. Bush's approval rating at the time was 33 percent. A Washington Post-ABC poll this week put his approval rating at 47 percent, basically equal to Obama's.
The museum exhibits cover major points of Bush's presidency and offer visitors an opportunity to decide how they would have responded to those challenges.
A central feature of the museum concerns the Sept. 11 attacks on the United States.
Obama has found himself pursuing some of the same policies that Bush began, such using drones on military targets and trying to overhaul U.S. immigration laws.
Obama is expected to speak at the dedication along with the former presidents.
"Regardless of the times when they served and their political and policy differences, there is a commonality of experience that the president believes binds them together," said White House spokesman Jay Carney.
After visiting Bush in Dallas on Thursday, Obama is scheduled to attend a memorial service at Baylor University in Waco, Texas, for the 14 people killed when a fertilizer plant exploded last week in West, Texas. (Reporting by Steve Holland; Editing by Karey Van Hall, Toni Reinhold and Lisa Shumaker)