A week ago, a major Ohio political leader told me: “Obama will never carry Ohio. Some people call it the Bradley effect, but how do you think the guys who work at the GM plant in Youngstown are going to vote? For a black? I don’t think so.”

[IMGCAP(1)]I didn’t believe it, but sure enough, race — nearly a forgotten factor in the Democratic presidential contest during Sen. Barack Obama’s (Ill.) long run of primary victories — evidently came back to help Sen. Hillary Rodham Clinton (N.Y.) win Ohio, Texas and Rhode Island on Tuesday.

And, unfortunately, it could be a factor again in Pennsylvania and — if Obama survives Clinton’s renewed onslaught to win the Democratic nomination — in the general election.

The “Bradley effect” — the tendency of voters to tell pollsters they’ll vote for an African-American candidate, then vote against him in the booth — certainly was evident in Ohio and Texas. Clinton out-performed pre-election polls by three points in Ohio, 1.5 in Texas and 8.3 in Rhode Island.

Moreover, exit polls in Ohio showed that fully 20 percent of primary voters acknowledged that “the race of the candidate” was “important” in deciding their vote. And Clinton won this group by a big margin — 59 percent to 39 percent.

Clearly, this represents white prejudice against Obama because he is an African-American and not the racial solidarity that regularly wins him 90 percent of the African-American vote.

It was the Ohio equivalent of Pennsylvania Gov. Ed Rendell’s observation in early February that, “you’ve got conservative whites here, and I think there are some whites who are probably not ready to vote for an African-American candidate.”

The Clinton campaign didn’t overtly stir up racial animosity in Ohio or Texas. It didn’t have to.

Rather, the Democratic contest was “racialized” back in January, when Sen. Clinton compared Obama to Dr. Martin Luther King Jr. and herself to President Lyndon Johnson, and when her husband, Bill, likened Obama’s South Carolina primary victory to the Rev. Jesse Jackson’s.

Before that, Obama was seeking to run as a “post-racial” candidate — the political equivalent of Tiger Woods.

Ever since the Clintons elevated the racial issue, however, blacks have been lining up strongly behind Obama and whites, to varying degrees, behind Clinton.

To be sure, Obama has been able to carry white males in many states, including working-class white males in some, enabling him to win 12 straight contests after Super Tuesday and amass a delegate lead over Clinton — perhaps an insurmountable one.

But the brilliant elections analyst Jay Cost, blogging for RealClearPolitics.com, has developed a convincing theory about the Democratic racial factor: Obama wins in states with majority-black Democratic turnout, like South Carolina, Georgia and Louisiana and in states with few blacks, like Wisconsin, Washington and Vermont.

He also has won in states with mixed populations where white family income is high, such as Maryland and Virginia.

But Clinton, Cost contends, wins in states where blacks constitute a major minority, but where average white income is lower, such as New Jersey, Massachusetts, Tennessee and Ohio.

So, in largely white Wisconsin, Obama carried white males by a margin of 63 percent to 34 percent. But in Ohio, Clinton won, 58 percent to 39 percent.

And, Clinton has been winning in states with a large Hispanic population, like California, New Mexico, Arizona and Texas. Hispanics and African-Americans often regard themselves as rivals for jobs, advancement and the status as America’s foremost minority.

In Texas, Latinos, 34 percent of the electorate, supported Clinton by a margin of 67 percent to 31 percent. Nineteen percent of voters said that a candidate’s race was an important factor, and Clinton carried this group by 52 percent to 47 percent.

In Rhode Island, another heavily working-class state, race was important to 20 percent of the electorate, and this group went 56 percent for Clinton.

Of course, many other factors besides race were involved in Clinton’s victories. White female solidarity was key. “NAFTA-gate,” raising questions about Obama’s sincerity on trade, was important in Ohio.

Also, media scrutiny of Obama ramped up after a “Saturday Night Live” skit lampooned its previous soft treatment. And Clinton’s “red phone” TV ad, questioning whether Obama has the experience to handle an international crisis, may have changed minds in Texas.

But race is a factor, and is likely to remain one, aiding Clinton in Pennsylvania and Sen. John McCain (R-Ariz.) in November, if Obama is the Democratic nominee.

McCain is too decent ever to raise the issue and the Republican National Committee is unlikely to repeat its counterproductive effort to race-bait former Rep. Harold Ford Jr. (D) in Tennessee last year.

But if bottom-dwelling slugs are willing to send out Internet messages lying about Obama’s religion, there’s probably nothing they won’t stoop to.