contend

non-transitive
1. to struggle in opposition:
to contend with the enemy for control of the port.
2. to strive in rivalry; compete; vie:
to contend for first prize.
3. to strive in debate; dispute earnestly:
to contend against falsehood.

transitive
4. to assert or maintain earnestly:
He contended that taxes were too high.

Source:  http://dictionary.reference.com/browse/contend?s=t