Because they have got a lot of screentime in season 8 and I think that they now are main characters.

Erm, no! You cant replace them!
You cant replace anything that has been so important for such a long time.

Mark's obviously TRYING to fill LP's void with Clay & Quinn. He's even given them numerous recycled scenes, and quotes that have already been used by LP. But please... Mark can try to distract us from the fact that LP are gone all he wants, but he'll NEVER be able to replace them. Especially not with a lame ass couple like Clay & Quinn lol, they'll never measure up <333

my thoughts exactly...at least to a certain degree...

Never ever!

Nah, I don't think so. I think Clay and Quinn as CHARACTERS are supposed to fill the void of two main characters...next to OTHER characters like Alex, Grubbs, Miranda etc.
I'm not sure though, we all know how big Mark's obsession with couples is so of course he had to throw 2 random newbies together! But it doesn't mean he tried to "replace" Leyton as a couple. He can't, of course.

That's probably Mark's intention... but they never will!-exactly what i wanted to say lol.
I realized that since the first moment i saw season 7 and saw Quinn/Clay will get together sooner or later.After they lost CMM and HB they needed 2 more characters so they went for 2 people who as well are very close to Nathan and Haley but we never saw them before.So here comes the sister and agent.I always had this impression that they came on the show as the new couple to fill a void that the last couple left but even if i am not a LP fan i am not buying this.I mean i would pick anytime LP over Quinn/Clay because i don't know i can't see any good scene between them and since Mark gives them just crap story-lines(stalker etc)what is there to love about them COMPARED to LP who had storyline and scenes and etc.Mark is obviously trying to do it but it won't work.

Exactly.

NEVER.

NEVER !