Paul Ryan rules out 2016 presidential bid

Mr Ryan's name was floated as a late contender if there is a contested convention in July, as doubts persist over the strength of the candidates.

If Donald Trump, John Kasich nor Ted Cruz is able to win 1,237 delegates, the convention will be contested.

The state-by-state primary contests, which come to New York next week, determine the number of delegates pledged to a particular candidate.

In 1886 former civil war general William Sherman set the gold standard for disavowing interest in serving as US president. "I will not accept if nominated and will not serve if elected," he bluntly stated.

Speaker of the House Paul Ryan may not reach Shermanesque levels of certainty with Tuesday's statement, but the move should put the latest round of rampant speculation and rumour-mongering to rest.

The Ryan presidential boomlet was largely a result of growing desperation among Republicans who see a presidential ticket headed by the epically unpopular Donald Trump as an unmitigated disaster and by absolutist Ted Cruz as only a slightly mitigated disaster.

Mr Ryan won't be their establishment-friendly "white knight", however, and there are few others out there with the stature to pull off such an unlikely convention coup.

Former candidate Mitt Romney? Wisconsin Governor Scott Walker? At this point, anyone other than Mr Cruz or Mr Trump - the two men who have slogged through the presidential season and won the votes and delegates - appears to be pure fantasy.