There are two really effective campaign ads blanketing the airwaves. One from each campaign. But only one of them is perhaps the most dangerous in its potential impact against its target. And Democrats better beware.

The Obama reelection campaign smacks around Mitt Romney for outsourcing jobs and having offshore bank accounts in tax havens as the presumptive Republican nominee warbles “America the Beautiful” in the background.

You have to laugh to keep from crying as you listen to Romney’s singing. But that aural assault combined with charges that the candidate shipped jobs to China, Mexico and India as the head of Bain Capital helps to cement doubts about the man who made his fortune in the world of private equity. Reminding viewers that the multi-millionaire had Swiss bank accounts and parked some of his fortune in tax havens, like the Cayman Islands and Bermuda, serves to highlight how the very rich are different from you and me.

But where the Obama ad is blunt, the offering from the Republican National Committee hits the president with a more-in-sorrow-than-in-anger attack ad. And every time I have seen it, I get an uneasy feeling. The same feeling you get when you think you hear water dripping somewhere but can’t find it. To ignore it is to risk disaster, which is exactly what will happen to Democrats if they ignore the power of this ad.

President Obama came to the White House with big plans. He’d halve the deficit. Strengthen the economy. Lower unemployment. What did we get? National Debt over 15 trillion and climbing. Unemployment above 8 percent for 40 straight months. An ongoing economic crisis with no end in sight. He tried. You tried. It’s OK to make a change.

All that stuff about what the president promised he’d do and didn’t isn’t what bothers me. Obama did make big plans. But inheriting a free-falling economy followed by a stubborn recovery coupled with congressional Republican recalcitrance, not to mention some backtracking on various things he promised, have made achieving many of those goals impossible. So, he and his campaign have to deal with that as best they can.

No, what bothers me is that last line spoken by the narrator as we see a black-and-white still image of a downward looking Obama.

He tried. You tried. It’s OK to make a change.

(See how readers are responding to this blog post in Rachel Manteuffel’s PostScript.)

Millions of Americans were swept up in the drama of the 2008 presidential contest and were proud to cast a ballot that helped elect the first African American president of the United States. Doing so was and will remain one of our nation’s crowning achievements. But there’s no denying that many of those same millions have soured on Obama because of what they believe he hasn’t been able to achieve. Yet, they are conflicted.

Poll after poll, including the just-released Wall Street Journal-NBC News poll, shows that while Obama gets low marks for his fiscal stewardship, people like him personally. And much more than Romney. The WSJ-NBC survey puts Obama’s favorable-unfavorable at 49 percent-43 percent and Romney’s at 35 percent-49 percent.

By telling potential voters “It’s OK to make a change,” the RNC is acknowledging all that I mention above. It’s OK to like the guy personally but not vote for him again. This is not a popularity contest. It’s OK to vote against the black guy. You gave him a shot. He gave it his best shot. He failed. And the most effective message is: “It’s OK to make a change” — and not be thought of as a racist.

Throughout Obama’s presidency, I’ve received more than a few e-mails and tweets from folks complaining that they are branded racist if they disagree with anything the president says or does. And it doesn’t help matters that I have seen more than a few e-mails and tweets from ardent Obama supporters doing exactly that. I have also seen instances of this on television and in print.

That’s why the “It’s OK to make a change” ad is the most dangerous for Obama’s reelection efforts. It give those few, yet crucial, undecided voters the pass they might be looking for to vote against Obama. So, squawk all you want about the unfairness of the “You didn’t build it” knock against Obama. It’s the “It’s OK to make a change” message that the campaign needs to counter as aggressively as the RNC is pushing it.