|Not reflective of all EU opinion?|
Well firstly, although the European parliament has a veto - it is the European Council (the member states) that first need to propose a candidate. David Cameron's best bet to block Juncker is therefore to form a blocking minority under so-called Qualified majority Voting (QMV) in the European Council. Here is how the votes stack up.
Under the current rules each of the 28 EU members is assigned a number of votes (the UK has 29). A smallest blocking minority weighs in at 93 votes. The European Council has its own calculator here allowing you to simulate the votes.
At the moment there are three states certain to attempt to block Juncker. The UK (29 votes), Sweden (10 votes) and Hungary (12 votes). They therefore have only 51 votes - 42 votes short.
There area a number of ways the remaining votes could be made up - the Netherlands (13 votes) is reportedly wary of Juncker, but it is increasingly clear that another big state needs to join the UK. Italy's Matteo Renzi isn't overly keen and France might try to play poker to get its own candidate in a key position, at Juncker's expense. Both Italy and France have 29 votes - one of them would be enough to muster a blocking minority.
Composition of possible blocking minorities under QMV
Also, it's very rare that EU leaders actually vote - the prevailing form of decision-making in the European Council (formally and informally) is unanimity. Merkel will want to give the impression of consensus. Having Cameron outvoted - and publicly humiliated - would rank as one of the most dramatic events in the EU in recent memory.
This remains anyone's game.