Ron Paul delegates at the Republican national convention in Tampa struck a note of noisy dissent for the second night running on Wednesday throwing another spanner in the party leadership's desire for a smooth trouble-free event.

Though the convention has nominated former Massachusetts governor Mitt Romney as its presidential candidate for 2012, an angry dispute with supporters of the libertarian-leaning Paul has repeatedly flared up.

In the months leading up to the convention the Texan congressman's defeated presidential campaign ran a "delegate strategy" to exploit arcane party rules and bring as many supporters to Tampa as possible. However, the attempt was largely stymied by party officials and Romney-backed lawyers, leaving many Paul supporters angry.

Rule changes pushed through for the 2016 nomination process – and aimed at preventing a repeat of the Paul delegate strategy – have also left many Paul backers and other conservative activists embittered.

As the convention prepared to listen to Romney's running mate Paul Ryan speak, a group of Maine delegates walked out of the convention hall in protest at their treatment. Shouting "Ron Paul! Ron Paul!" they marched through the convention hall, engaging in fierce arguments with Romney supporters.

Video of the moment quickly circulated on Twitter and showed Paul backers and Romney fans trying to drown each other out with chants. Some Paul fans shouted "This convention is a farce" and "Shame on them." Others sang: "As Maine goes, so goes the nation."

Though the fight over Paul's supporters is a sideshow that has little real impact on the Romney team, it is no doubt an unwelcome distraction as the campaign seeks to present a united party to the nation and paint Romney as a sympathetic, warm president-in-waiting.

It also does not seem to be a dispute that will settle down. Before the convention began Paul supporters held numerous events, including a mass rally at the Sun Dome sports arena. Ever since then Paul supporters have dotted downtown Tampa on each day of the convention wielding Paul campaign posters. Many of them, including some convention delegates, openly talk of not planning to vote for Romney in the coming November election.

Ironically the latest protest came as the convention actually paid a video tribute to Paul, who is now retiring after 12 terms in Congress and several unsuccessful runs for the White House. The video paid tribute to Paul's hard-line fiscal conservatism but made no mention of his foreign policy, which is focused on bringing American troops home from abroad and closing foreign bases.

It was then followed by a speech from Kentucky senator Rand Paul, who unlike his father, has publicly endorsed Romney. Paul is widely seen as a possible presidential candidate, following in his father's footsteps and sharing many of his views. When Paul spoke at the Sun Dome rally he was greeted with cries of "Paul 16!" referring to the 2016 race. However, Paul played by the rules in his convention speech and endorsed Romney.

But his speech also struck many of the key points that Ron Paul runs on, including advocating military spending cuts that are usually anathema to Republican audiences. He also spoke about the risks of losing vital civil liberties in the name of fighting terrorism: another favourite topic for his father.

"We must never ever trade our liberty for any fleeting promise of security," Rand Paul said.