NEW YORK CITY - SEPTEMBER 3 2015: Republican candidate for president Donald Trump announced he had signed a pledge not to run as an independent candidate should he fail to win the party's nomination in 2016.

How Undecided Republican Voters Say to Take on Donald Trump

Last night in Atlanta, I talked to 35 undecided Republican primary voters. The voters on the panel were proportioned based on both demographics and geography to model the voting turnout of the Republican Presidential primary. Every one of the undecideds had voted in prior Presidential primaries and intends to vote in the 2016 primary. They are the likeliest of likely voters, but also remain undecided.

I explained much of the source of their being undecided here.

One of the things I did not cover in that prior piece was attacks on Donald Trump and how to beat him. We spent time talking about that last night.

The panel of voters was pretty evenly divided on Trump. A majority said they liked he was forcing topics to be discussed, but a majority also was pretty sure they could not support him. At this point, in fact, most polls show that undecided voters now are least likely to back Trump.

I played them the advertisement from the John Kasich Super PAC with statements made by Trump. The panel, surprisingly, was completely put off. Even people who adamantly did not like Trump said the ad was ineffective because it focused on the outlandish stuff Trump said, which, the panel agreed, was why Trump was actually doing well. He was entertaining and not a traditional politician.

The consensus of the undecided voters was that the only way to take on Donald Trump and beat him was on both his prior record and his lack of policy depth now. These voters thought his prior relationship with both the Clintons and the Democrats was fair game. One voter said Trump should just be ignored, but most of the voters agreed that he should be challenged on his prior record. Several commented during commercial break that they knew people who had no idea Trump had voted for Barack Obama or given money to Nancy Pelosi.

The line of attack on Trump the undecided voters suggested seems similar to the line of attack from Club for Growth. The Club hit Trump’s record and, while it did not pull people away from Trump in Iowa, seems very likely to have been the source of freezing Trump’s ceiling.

Again, it is worth pointing out that these undecided voters, split on the merits of Trump’s candidacy, were almost unanimous that attacking Trump on his outlandishness would do no good. They think his record as a Democrat and lack of policy depth are the only avenue to target Trump.

The other Republicans might want to take notice.