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Former Florida Gov. Jeb Bush offered Mitt Romney some advice this morning on "Good Morning America" just hours before the GOP presidential nominee will make the most important speech of his political career: Show your heart.

"It's hard for him to show his heart. I respect that. I was brought up being told not to brag, not to open up and show your frailties and show your emotions, but he has to," Bush told me. "Where it matters is connecting with other people's concerns. I don't think he has to be like this New Age kind of guy all of a sudden. He's not going to be that way."

Romney will address the Republican National Convention this evening in Tampa and formally accept the Republican nomination for president. The speech offers the former governor of Massachusetts - often attacked as wooden by his critics - a chance to boost his favorability among voters, which seems critical given that a new ABC News/ Washington Post poll found that Romney is the least popular major-party nominee since 1984.

Bush - both the son and brother to former presidents - told me during the interview that connecting emotionally to people is the first step Romney must take in order to make a case for himself as a viable alternative to President Obama.

"It's important to connect emotionally. That gives you the chance to allow people in…he has to do that for sure," Bush said. "But it doesn't have to be, the standards that the observers will have will be so high and so psycho-babbly that he won't be able to reach that for sure but connecting well and he has a great chance tonight to offer an alternative. Not just to point out the president's failings but to offer an alternative that lifts the spirits of the country."

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