"likely mainly" is an acceptable phrase in written English.
You can use it to emphasize that something is probably mostly or probably primarily the case. For example: "The recent recession is likely mainly caused by economic over-expansion."
Her confirmation is considered highly likely, mainly because of the Senate's practice of confirming members to multimember agencies in pairs, one Democrat and one Republican.
In Washington's close-in northern and western suburbs, from central Fairfax County through southern Montgomery and northern Anne Arundel counties, one to three inches are most likely, mainly on grassy areas.
This work shows that contrary to common assumption the agents investigated are unlikely to have acted chemically at the flame front, but most likely, mainly cooled the flame and changed the stoichiometry, i.e. the ratio of components of the flammable mixture.
Acts inflaming some sections of the Muslim population came at a time when attacks on the West were highly likely mainly due to the sheer numbers of young Muslims from the West who had gone to take part in jihad in Syria and Iraq.
Thus, symphyseal fusion in primates is most likely mainly linked to the timing and recruitment of transversely directed forces from the balancing-side deep masseter (Hylander et al. Am. J. Phys. Anthropol. 112 469-492).
The R3+O1.5 components important in natural olivines are likely mainly Fe3+O1.5 and Cr3+O1.5 (Tollan et al. 2015; Blanchard et al. 2017), which are both redox-sensitive and depend on fO2.
Since nematode-parasitic fungi do not produce trapping devices, they likely rely mainly on the extracellular enzymes (including subtilisin-like serine protease) as virulence factors to penetrate and digest nematode cuticles.
Both novels will likely appeal mainly to die-hard Harry Potter fans.
But with less than three weeks until Oct. 7, a court spokesman said a determination was likely soon, mainly so the dispute could be appealed to the United States Supreme Court if necessary.
The upcoming glitch is likely to mainly affect mostly older GPS receivers or those lacking recent updates to their 'firmware' — software programmed into a device's permanent memory — that ensure devices are not confused by the rollover.
Some sleet and snow is likely too, mainly on higher ground, the hills and mountains.
