They looked like running mates - all square jaws, broad shoulders, and firm handshakes - when they stepped off a bus to the strains of “The Battle Hymn of the Republic’’ playing on the steps of Needham Town Hall.

It was 2004, and it looked as if Scott Brown, a little-known state representative from Wrentham who was running for state Senate, and Mitt Romney, his political patron and the governor of Massachusetts, would be leading an effort to change the entrenched, Democratic culture of Beacon Hill.

“To get that job done, I need to get Scott Brown on the reform team,’’ Romney declared, as the crowd burst into chants of “We want Brown!’’

At that point, they agreed on virtually every major issue - opposing gay marriage, abolishing bilingual education, rolling back taxes, instituting the death penalty, cutting budgetary waste and inefficiency.

But despite the stage they shared that day, Brown and Romney never developed more than a passing political partnership, according to friends and associates. As Brown’s star has risen as a moderate proud of his bipartisan appeal, and Romney has worked hard to court the Republican base in his bids for the presidency, their paths have diverged, and their relationship has become more complicated as a result.

Brown no longer features Romney on his website or in his political ads, as he did in that 2004 race. Now, he advertises the three times when he has stood behind President Obama at the White House as Obama has signed Brown’s bills into law.

Brown’s campaign is also working subtly to distance him from Romney, whose sagging popularity in Massachusetts could make him a liability for Brown.