State Sen. Abel Maldonado, a Republican legislator from the Central Coast, had the Democrats over a budget barrel and extracted from them the ultimate insider's deal -- they would put three of his pet ideas on the 2010 ballot (as constitutional amendments) in return for his deciding vote on the budget. You have to admire Maldonado's moxie even as you're appalled at this latest example of how broken the legislative process in Sacramento has become.

So what was on the senator's personal wish list? Two of the measures relate to curbing legislators' pay; the third would install a "top-two" primary system in California. Maldonado likes to call this an "open primary," but that's just for propaganda purposes. As political scientists understand these matters, an open primary is one in which voters can vote in the primary of any party they wish, but only in that party's primary for all races on the ballot. Then the primary winner for each party appears on the November ballot in a multiparty, multi-candidate field.

That's different from what's called a "blanket primary," which California used in the 1990s until a U.S. Supreme Court decision led to its abolition. Under this scheme, voters select a candidate from any party in each race, and all parties' primary winners appear on the November ballot. But the court ruled that because primaries are a political party's private affair, they cannot be forced to use a blanket primary. California's parties opted out of the blanket primary.

Maldonado's top-two primary is different still. Under his method, the nominees from all political parties, including multiple candidates from the same party, compete against each other in a single primary free-for-all. Only the top two finishers overall advance to the November election. Those two final candidates could be from the same political party, and rarely are they from a third party or an independent candidate.

Proponents of the top-two primary say it will give voters more choice, create more competition, elect more moderate legislators and guard against spoiler candidates. But will it deliver?

A top-two primary certainly would give voters more choice during the primary election, but it would reduce voters' choices in the November election -- to only two candidates, no matter how many parties put up how many candidates in the primary. That means in the general election, which is when most voters participate, the ballot will contain a dramatically reduced field.

But that's not all. In a very liberal district, say an urban area like Los Angeles, the top two candidates in November likely would be two Democrats; in a conservative district, the top two probably would be Republicans. Third-party candidates and independents almost never would appear on the November ballot. Once again, choice is reduced.

To understand if the top-two primary plan might result in more competitive races, I examined elections in the state of Washington, which used the top-two primary for its 2008 state legislative elections. Here's what I found:

With 98 state House races, only five were won by a competitive margin (defined as a 4-percentage-point difference between the top two candidates). Sixty-five races (66%) were won by landslide margins of 20 points or higher. In the 26 state Senate races, the results were very similar, with 62% won by landslides and only two races fitting into the competitive category. That's a level of competition that hasn't changed much from past Washington results, and is no better than what we have now in California.

In terms of electing more moderates, the Washington elections were a failure. The term "moderate" is a relative one, with different definitions from state to state, so a better way to examine this is to look for how many opportunities were available for moderates to get elected. One way to do that is to see how often the system pitted two Democrats against each other in November, or two Republicans, so that the voters from the other party could act as a moderating influence against either the most conservative Republican or the most liberal Democrat.

In Washington's House races, only six out of 98 (6%) had two candidates from the same party, and in the Senate, two out of 26 races (8%) did. So in only a handful of races did moderates have an improved opportunity to get elected.

On a positive note, for the handful of races in Washington decided by competitive margins, candidates didn't have to worry about spoiler third-party candidates. But is essentially banning third parties from participating in November elections really the best way to achieve this? A better way would be to use "instant runoff" voting, under which you could rank a first, second and third choice from among all comers, and, if your first choice doesn't win, your vote goes to your second choice as your "runoff" vote. This would rule out spoiler candidates but would preserve voters' choices.

Results from Washington state's elections show that a top-two primary did not result in more competition or many opportunities for moderate candidates to get elected. It gave voters more choice in the primary, but at the cost of reducing their choices in the November election. The winners won by majorities and it got rid of the spoiler problem, but at the price of greatly restricting third parties from the November ballot.

When it comes to reform, be careful what you ask for.