[EM] Two round methods

[Kevin Venzke]

I see a need for non-eliminative two-round methods. I like the idea that the first round places
a "default winner" or "guy to beat" in the electorate's consciousness, so that, possibly, voters
would consider offering more of their preferences in the second round.

A difficult thing is to make sure it is worthwhile to seriously compete in the first round, and
also, relatedly, that the second round should not simply reverse the outcome of the first round
based on small changes in participation rate.

Here's an idea based on two-round Approval. Let's call it NETRA.

1. If the first round winner ("FRW") has majority approval, he is elected. End.
2. Otherwise hold the second round with all the same candidates. If this new winner has
majority approval *and* the FRW does *not* have majority approval, then the new winner is
elected. Otherwise the FRW wins.

So in the second round the FRW is given a couple of perks. If he raises his vote to a majority,
or if (again) no one can get a majority, he doesn't have to beat anyone. He can prevail based
on his first victory.

This has two purposes: It should be desirable to be the FRW. And the FRW's advantage
should increase the electorate's assessment of the FRW's odds, so that hopefully the second
round serves to tell us whether there is a candidate preferred by the voters to the FRW. (It
is an approval ballot in form, but what I'm actually after is the FRW's pairwise contests.)

Main concerns:
1. If candidates were to conclude that being the FRW is overall a bad situation. I'm not
sure how likely this is, given that a first-round majority is an auto-win.
2. It's still quite possible that a majority opposing the FRW in the second round would fail
to agree to get behind any single candidate. Then a lack of an approval majority in the first
round would simply be repeated in the second, for no benefit. (There is, I suppose, the 
additional confirmation, for all to see, that there is no majority willing to unite against the
FRW... It also confirms that the winner couldn't attract a majority.)

Kevin