Seeking to make President Bush’s plan to overhaul Social Security an issue in Sen. Rick Santorum’s (R-Pa.) re-election bid, Democratic leaders will hold a rally in Pittsburgh next week — the second such event they have staged in Pennsylvania in less than two months.

The Pittsburgh rally is part of a two-day barnstorming tour by Senate Democratic leaders, with other stops scheduled for Rhode Island and Ohio. All three states are represented by incumbent Republicans running for re-election in 2006.

Publicly, the tour is being billed as an effort to criticize Bush’s effort to retool Social Security. But Democrats acknowledge there is a political calculation at stake when they choose what states to visit.

In addition to Santorum, who is arguably the most vulnerable Republican Senator up for re-election next year, Democrats will try to turn the heat up on Republican Sens. Lincoln Chafee (R.I.) and Mike DeWine (Ohio) — two Senators whose states are home to sizable Democratic constituencies.

“The Senators from these states are either advocating cutting benefits, as in the case of Rick Santorum, or are playing footsie with the Republican leadership instead of decrying this bad plan, as in the case of Sens. DeWine and Chafee,” said Phil Singer, spokesman for the Democratic Senatorial Campaign Committee. “The bottom line is the voters in these states know where their Senators stand on these issues.”

Senate Minority Whip Harry Reid (D-Nev.) added, “These are places where we need to talk about it.”

Reid and several of his Democratic colleagues held a similar 48-hour tour in early March, including events in New York City, Philadelphia, Arizona and Las Vegas. On the first tour, Democrats sought to pressure Santorum and Sen. Jon Kyl (R-Ariz.). Santorum is chairman of the Senate Republican Conference and Kyl is the chairman of the Republican Policy Committee.

Despite Democratic wishes, Kyl at this point is not in serious danger of losing re-election. However, Santorum is expected to face a difficult re-election battle against likely Democratic nominee Bob Casey Jr., the state treasurer and son of a former Pennsylvania governor.

Congressional Democrats and their K Street allies privately acknowledge that Santorum, who’s known for his unabashed social and fiscal conservatism, is their No. 1 target next year.

“Rick Santorum remains No. 1, No. 2 and No. 3 on our list of least-favorite Members, and the fact is, this won’t be the last time we will show up in Pennsylvania to talk about Social Security,” the senior Democratic aide said.

Santorum said he is prepared for the Democratic criticism, but charged that Democrats are not offering up any solutions.

“Maybe they are going to announce in Pittsburgh what their solutions are to the problem, instead of complaining that there is not a problem and Republican solutions are not what they favor,” he said.

And the Pennsylvanian noted he expects the Democratic attacks on him to increase as the 2006 election season heats up.

“I am sure they will be back many, many times and on many, many different issues and I am looking forward to hearing their ideas, and how they are going to solve the problems,” he said.

DeWine, too, said he has heard little from Democrats about how to fix Social Security, a program that Republicans say is in “crisis.” Democrats roundly dispute this claim and argue that Republicans should focus on more pressing domestic needs such as health care.

DeWine said that so far, he thinks “the president has done a good job convincing people that there is a problem, and [that] we have to do something.” But the Ohio Senator noted Democratic support is crucial for reform to be accepted.

DeWine acknowledged that he is “getting mixed reaction about whether people want to do a personal savings account within Social Security” — the course of action that Bush deems essential. But DeWine said he is open to discussions about creating a personal savings account outside of the Social Security system.

“It seems to me a Democrat would not object to that,” DeWine said. “We ought to be able to talk about something like that.”

DeWine said the trouble is that his Democratic counterparts are refusing to negotiate in good faith.

“All I am saying is, ‘Let’s get this out and get some bipartisan discussion,’” DeWine said. “But we can’t get the Democrats engaged in it yet. That is the problem.”

Democrats said next week’s rallies will be critical in their effort to try to defeat Bush on Social Security. Democrats note that Republicans have an institutional advantage because the GOP controls the White House bully pulpit. They also point to Bush’s own barnstorming tour, which has drawn extensive media coverage.

“The president is putting a lot of miles on Air Force One, and he is moving around the country on this issue,” said Senate Democratic Policy Committee Chairman Byron Dorgan (N.D.).

Organizers are still finalizing the details of the tour, but in addition to Democratic leaders, Sen. Jack Reed (D-R.I.) and former Sen. John Glenn (D-Ohio) have been penciled in to participate at rallies in their respective states, Democratic sources said. Democrats will kick off the tour at an event next Friday in Washington, D.C.