and you have to be a pretty pathetic sheep to be herded around by a lapdog.
The invasion wasn't universally condemned; probably a small majority of people were against it at the time, and the number who think it was wrong has gradually increased since then. But Blair is articulate, as you say, and many people didn't realise then how much he was lying.
In particular, Labour MPs depend on him for the advancement of their career. The government has a lot (about 100? Anyone?) of positions to give to MPs in various departments at various levels. Disobey the PM on a serious matter, and they could lose the position (in many cases meaning a pay cut, as well as loss of influence, power, and standing in the party). Blair has assembled the largest pack of non-elected 'advisors' around him any PM ever has, and they are ruthless and unforgiving (Alistair Campbell is the outstanding example, but he's not the only one - it was he who used outing David Kelly to, as he put it, 'fuck' the BBC). Cross them, and you may never get any government post again - unless there's a complete change of people.
So, most Labour MPs voted for invasion:
http://www.publicwhip.org.uk/division.php?date=2003-03-18&number=117247 for for the invasion; 139 against it; 28 abstained. Since the vast majority of the Conservatives also voted for invasion, he had the effective backing of the House of Commons.
Constitutionally, the PM wields enormous power - he can take the country to war without consulting Parliament (the vote on Iraq was actually unnecessary, and was a concession to the high feeling against it), and do most other things the US President can do (he is often doing them in the Queen's name, but the monarch hasn't got involved in major political affairs since George III - I think she'd only intervene if he did something like invade Belgium).
Why does Blair walk around with his nose embedded in the Chimp's arse? A very good question. Rory Bremner, a comedian and impressionist, suggested last night it was to make sure his autobiography sold well in the US when he retires. Like all good jokes, there could be some truth in it - Blair does seem drawn to the rich and famous (and it has been suggested he'll go to work for the Carlyle group when he stops being PM). I think he's drawn to power - and when he can't get hold of it himself, as in the case of a huge business, like Rupert Murdoch, or the American presidency, he just fawns over it instead. He thinks by doing what the powerful say, he can influence them. He's wrong.